package demo;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 石方旭
 * Date: 2022-07-05
 * Time: 11:35
 */
public class MyLinkedList {

    static class ListNode{
        public int val;
        public ListNode prev;//前驱
        public ListNode next;//后继

        public ListNode(int val){
            this.val = val;
        }
    }

    public ListNode head;//头
    public ListNode last;//尾

    //头插法
    public void addFirst(int data){
         ListNode node = new ListNode(data);
         if(head==null){
             head = node;
             last = node;
         }else {
             node.next = head;
             head.prev = node;
             head = node;
         }
    }
    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
          if(head==null){
              head = node;
              last = node;
          }else {
              last.next = node;
              node.prev = last;
              last = node;
          }
    }
    //任意位置插入,第一个数据节点为0号下标
    public boolean addIndex(int index,int data){
        if(index<0||index>size()){
            System.out.println("该下标不合法！！！");
            return false;
        }
        if(index==0){
            addFirst(data);
            return true;
        }
        if(index==size()){
            addLast(data);
            return true;
        }
        ListNode node = new ListNode(data);
        ListNode cur = head;
        while(index!=0){
            cur = cur.next;
            index--;
        }
        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;

        return true;
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = head;
        while(cur!=null){
            if(cur.val==key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
         if(head==null){
             System.out.println("该链表为空，无法删除");
             return;
         }
         ListNode cur = head;
         while(cur!=null){
             if(cur.val==key) {
                 //此时cur为要删除的节点
                 if(cur==head){
                     head = head.next;
                 }else{
                     cur.prev.next = cur.next;
                     if(cur.next==null){
                         break;
                     }
                     cur.next.prev = cur.prev;
                     return;
                 }
             }
             cur = cur.next;
         }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        if(head==null){
            System.out.println("该链表为空，无法删除");
            return;
        }
        ListNode cur = head;
        while(cur!=null){
            if(cur.val==key) {
                //此时cur为要删除的节点
                if(cur==head){
                    head = head.next;
                }else{
                    cur.prev.next = cur.next;
                    if(cur.next==null){
                        break;
                    }
                    cur.next.prev = cur.prev;
                }
            }
            cur = cur.next;
        }
    }
    //得到单链表的长度
    public int size(){
        ListNode cur = head;
        int sz =0;
        while(cur!=null){
            sz++;
            cur = cur.next;
        }
        return sz;
    }
    public void display(){
        ListNode cur = head;
        while(cur!=null){
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
    }
    public void clear(){
         ListNode cur = head;
         while(cur!=null){
             ListNode curNext = cur.next;
             cur.next=null;
             cur.prev = null;
             cur = curNext;
         }
         head = null;
    }

}
